JP2014509576A - Tread having at least one corrugated groove and manufacturing method thereof - Google Patents

Abstract

  The present invention is a heavy vehicle tire having a tread (2) having a total thickness E and a total volume V. The tread has a rolling surface (200) that contacts a road surface, and the tread extends in a main direction. Having at least one cavity or groove (5), the cavity or groove (5) being defined by side walls (54) connected to each other by a bottom (53), the cavity or groove having a cross-section, The innermost part of the bottom (53) of the cavity defines a bottom line (530), and the tread has a plurality of open sections (51) and a plurality of closed sections on the rolling surface when each cavity or groove is new. (52), wherein the closed sections are connected to the open sections and are arranged at intervals, each closed section being spaced from the rolling surface by a rubber bridge, cavity The location on the groove bottom line (530) is located at a distance between the minimum distance Dm and the maximum distance DM with respect to the rolling surface, and each cavity or groove bottom line (530) is corrugated. And relates to a tire characterized in that the positive amplitude of the waveform is equal to the difference (DM-Dm).

Description

  The present invention relates to a tread for a tire attached to a heavy-duty transport vehicle, and more particularly to a tread pattern of these treads.

  In rainy weather, it is necessary to remove the water in the contact area between each tire and the road surface as quickly as possible, the purpose of which is to ensure contact between the tread components and this road surface It is in. In order to achieve this, grooves are formed on the tread which, due to their dimensions (depth and width), remain open in the contact patch for contact with the road surface, thus Water that is not pushed forward and around the sides of the tire can be washed away.

  The grooves can have any shape in the plane of the line when viewed in cross-section and along the tread surface, and the grooves can be directed in any direction. The expression "tracking lines along the tread surface" is the average geometric line followed by the corner edges that these grooves form on the tread surface.

  In the case of tires for steering heavy axles or steering support axles, the treads of these tires have a total depth of tread (the purpose of allowing the grooves to be partially regenerated by the groove reshaping operation). It is customary to have a longitudinal groove equal to or substantially equal to (not including the thickness of the tread that may be provided). Generally, this depth is 13-18 mm for these axles. In the case of a tire intended for a driven axle, the groove depth may be larger than this and as large as 24 mm. The expression “total thickness of the tread” is used herein to mean the total thickness of the wearable material before the tire must be replaced by retreading or must be reconditioned. doing.

For such prior art tires, the total void ratio is typically 15-25% of the tread volume that becomes worn during operation. These tires have been found to have a relatively large effective void volume in the contact patch in the new state, and this void volume opening on the tread surface in the contact patch is, for example, that of a tire of size 315 / 70R22.5. In this case, the average is on the order of 100 cm ³ . In the case of the tire in question, this value is obtained in particular for its nominal inflation pressure and static load conditions as defined in the ETRTO standard.

  Furthermore, it is customary to form rubber edge corners on the tread surface to improve the grip between the tire and the road surface. In order to form such edge corners, sipes are made, which are applied when the wall of material defining each sipe passes through a contact patch where the tire contacts the road surface under normal load conditions. Thin cuts with an average width such that the walls of the material can at least partially contact each other, thereby limiting the reduction in stiffness associated with the presence of sipes. These sipes may be of a depth equal to or less than the thickness of the tread to be worn.

  Grooves or, generally speaking, cavities are essential for draining water, but the resulting reduction in the surface area of the material can have a significant adverse effect on tread wear rate performance, Thus, the useful life of the tire may be reduced as a result of increased wear rates. Other performance aspects related to the tire, particularly its behavior, road noise and rolling resistance, may also be adversely affected. It has also been found that these grooves formed to have a working depth equal to the height of the tread to be worn can cause durability problems. Under certain operating conditions, foreign objects, such as stones, may remain in these grooves and attack the bottom of these grooves, so that breaks may appear in the rubber. is there. It has also been observed that operations involving getting on and off various obstacles can cause breakage at the bottom of certain grooves, particularly at the bottom located near the side edges of the tread.

  The presence of grooves in the tread is known to cause a reduction in the compression and shear stiffness of the tread. This is because these grooves define portions of material that are easily deformed compared to portions defined by sipes where the walls can contact each other. This decrease in stiffness in the presence of grooves increases the degree of deformation and decreases the wear resistance of the tread, and a large amount of wear is observed for the observed set distance (this corresponds to an increase in the tread wear rate). doing). In addition, increased rolling resistance and thus increased fuel consumption of vehicles equipped with such tires are the result of increased hysteresis losses associated with deformation cycles of the tread components.

  With the thickness that these treads need to be in mind, ordinary tires used in heavy-duty vehicles define the choice of rubber material used in the tread near the edge of the tread, especially with limited hysteresis Having an operating temperature that requires the use of the composition to be prepared.

  International Publication No. 03/097384 (A1) pamphlet discloses a heavy-duty vehicle tire having a tread with a groove opened to the tread surface and a cavity located under the tread surface in a new state. Each of these cavities has a top bus that follows the waveform profile.

Definition

The tread pattern of the tread in this specification has the geometric shape of the part of the tread that comes into contact with the road surface, and this tread pattern is mutually connected by notches (grooves, sipes, wells, cavities). Made of defined raised elements.
The total volume of the tread is the total volume of material that can be worn away during operation before the tire must be removed in order to either regenerate the tire tread by renewal or replace it with a new tire. be equivalent to.

  The total void (or cavity) volume of the tread is equal to the sum of all void volumes that are open or not open on the tread surface in the new state. Void means a groove, well or any type of cavity so that the cavity opens into the contact patch for contact with the road surface and contributes to drainage at the contact patch at one point or at another time. It has become.

  The block is a raised element formed on the tread, which is defined by a void or groove, and the raised element has a side wall and a contact face adapted to contact the road surface during operation.

  The equator intermediate plane is a plane that passes through all the points on the tire that are perpendicular to the rotation axis of the tire and that are radially farthest from the rotation axis. This equatorial plane divides the tire into two approximately equal halves to varying degrees.

  The radial direction means a direction perpendicular to the rotation axis of the tire (this direction coincides with the thickness direction of the tread).

  The axial direction means a direction parallel to the rotation axis of the tire.

  The circumferential direction means a direction perpendicular to both the axial direction and the radial direction.

  As usual, this specification uses the terms “elastomer” and “rubber” interchangeably, and the two terms are interchangeable.

International Publication No. 03/097384 (A1) Pamphlet

  The present invention relates to a tread for a tire adapted to be attached to a heavy-duty transport vehicle, and by using a tread pattern of one type of tread pattern, the wear resistance, the rolling resistance performance, The object is to provide a tread that allows a significant and simultaneous improvement in grip performance on the road surface, in particular resistance to mechanical attack on the bottom of the groove near the side edges.

For this purpose, one gist of the present invention is a heavy-duty vehicle tire having a tread with a total thickness E and a total volume V, the tread having a tread surface that comes into contact with the road surface, Tread
-Having at least one cavity or groove continuous in the main direction, the cavity or groove defined by side walls connected to each other by a bottom, the cavity or groove having a cross-section, inside the bottom of each cavity The farthest point toward the
Each cavity or groove has a plurality of open sections and a plurality of closed sections that are open on the tread surface in a new state, and the closed sections connected to the open sections are arranged every other; In the tire, each closed section is spaced from the tread surface by a rubber bridge,
The point on the bottom of the cavity or groove is located at a distance between the minimum distance Dm and the maximum distance DM, and the distance measured on the tread in the new state relative to the tread surface is the total tread At most equal to thickness E,
-The bottom line of each cavity or groove is equal to the difference in the positive amplitude (DM-Dm) and E. T. T. et al. R. T. T. et al. O. Follow the waveform geometry along a wavelength shorter than the average length of the contact patch measured under the conditions of use specified in the standard,
The rubber bridge formed between each closed section and the tread surface is in a tire characterized by being continuous.

  Preferably, the minimum distance Dm between the bottom of the corrugated groove and the tread surface is equal to at least 25% of the total thickness E of the tread.

  The term “waveform” is used herein to zigzag between two levels: minimum distance (at a distance Dm from the tread surface) and maximum distance (at the distance DM from the same tread surface). Or even vibrate.

  E. T.A. R. T.A. O. The use conditions specify the reference inflation corresponding to the load resistance of the tire as supported by the bottom angular load of the tire and its speed code. The contact patch for contact with the road surface is statically defined with respect to the tire, from which the average contact patch distance is calculated.

  The expression “located at a distance between the minimum distance Dm and the maximum distance DM” is used herein to refer to a location on the bottom of one cavity located at a distance equal to the minimum distance Dm and the same bottom. The other part of the line is located at a distance equal to the maximum distance DM, the other part on the same bottom is located at a distance longer than the minimum distance Dm, and the other part is maximum with respect to the tread surface. It should be understood that it means being located at a distance shorter than the distance DM.

  “Waveforms along a wavelength whose amplitude is equal to the difference (DM−Dm) and shorter than the average length of the contact patch measured under the use conditions defined in the ETROTO standard for new tires The expression “geometrical shape” refers to a plurality of cavity sections open to the surface of the tread, at least when the tread is new (some of these sections are called “open”). In contrast, the other section called “closed” means that when the tread is new and thus in a non-wearing state, the whole is located below the tread surface. Should be understood. The open sections and the closed sections are arranged alternately. The closed section opens on the tread surface only when the tread is partially worn. Thus, a kind of groove is formed, and its corrugated geometry is such that when the tread is new, the groove is open on the tread surface in some places and the groove between these open places is in the tread. (This is equivalent to saying that this continuous cavity opens discontinuously on the tread surface).

  Each continuous and corrugated cavity or groove present in the thickness of the tread has an average cross section, and the surface area of the cross section is constant or averaged to allow fluid to flow along the groove. It is possible to have variation around the center.

  The tread of the present invention creates a continuous bridge of rubber that extends radially over the top of each closed section of each corrugated groove, which occurs as a result of striking against the side edges of the tread or at least the tread. This is a particularly effective way to increase the resistance to deformation caused by driving over obstacles when the is new. A continuous bridge of rubber is to be understood as meaning that the material located radially outward of each closed section does not have sipes or grooves extending in the same direction as the main orientation of the cavity.

  The cavities of the present invention may be formed in a major direction that is the circumferential direction of the tire, in which case such cavities extend around the tire or alternatively in an oblique or even lateral direction. . Of course, combinations of different orientations on the same tire are possible just as the cavities can be formed at various depths in the tread.

The invention also provides a method of obtaining a tread having at least one continuous corrugated cavity or groove, the method comprising:
-Adjusting the unvulcanized band of rubber;
-Incorporating at least one insert into the rubber band with a geometric shape that is corrugated at least in the depth of the tread;
-Forming and vulcanizing the tread band;
-At least partially removing each insert to form at least one continuous corrugated cavity or groove.

  One approach to forming such a tread is to incorporate the insert into an unvulcanized band, which is consistent with the dimensional characteristics of the corrugated continuous cavity to be obtained. The insert is positioned in the unvulcanized band in a corrugated geometric shape from the outer surface of the new tread or at least near the outer surface. This operation may be performed by a co-extrusion operation using an extruder having a main extrusion head, and at least one sub head for extruding the insert is provided inside the extrusion head. The head is provided with means for moving it in the desired corrugated direction of the cavity.

  This coextrusion operation is performed using a vehicle tire tread forming machine similar to the machine described in the patent application filed in 2010 but not yet published as of the filing date of the present application. Is good.

According to the earlier patent application, this machine is
-Means for extruding an unvulcanized band of rubber;
-Means for forming at least one recess in the tread with a geometric shape that is corrugated at least in the depth of the tread;
-Means for receiving a reel of strips to form an insert;
-Including a recess or means for inserting a strip from the reel into each recess.

  Of course, this insert needs to be made of a material that can be removed from the tread after vulcanization so that a continuous and corrugated cavity appears. Thus, it is possible to use a material with a tensile strength that can then be removed by pulling such material after curing and before the tire is used.

  Another means is to use a material that can be removed by dissolution upon contact with water as soon as it is at least partially visible at the tread surface to form the insert. After molding and vulcanization, water is introduced into the vicinity of each insert until the insert is completely dissolved. This may occur following partial wear that brings the insert into contact with the tread surface.

  Another possible means is to form the insert with a powder material that can be removed under the influence of centrifugal force as soon as the tire begins to rotate due to its non-stickiness.

  Another possible means is to use materials that cannot be vulcanized (saturated materials that do not contain double bonds) and that can be removed after molding to form continuous grooves.

  It is advantageous if the insert used to form the corrugated groove can be cut in advance to a length shorter than the total length of the tread. This means facilitates the next removal of the tread insert after molding.

  Of course, a combination of these various means can be employed depending on the cross section of the cavity, the amplitude of its waveform and its average wavelength. Once molded and vulcanized, the tread is slightly machined to expose the open section of the cavity on the tread surface if necessary, ie if one or more inserts are not visible at the tread surface. It can be processed. In order to make the insert clearly visible, it is possible to plan to color the insert in a color different from the tread color.

  In another equally advantageous form, an insert in the form of a hollow tube may be introduced into the tread, such tube having a continuous cavity therein after molding and vulcanization. The hollow tube may be made of a rubber-based material containing at least one elastomer as a main component, and the rubber-based material may or may not be the same as the material of the tread itself. Well, the material is further shaped to remain in place after partial wear exposing the insert. It is advisable to provide a means to maintain the pressure inside the tube during molding (either by filling the tube with liquid that can be removed after molding or by filling the tube with pressurized gas) to mold the cavity. It can be said that there is.

  In another embodiment, the tube may be made of a material different from that of the tread. For example, the material may have improved tear resistance compared to the same performance of the tread component. Plastic materials may be used for this purpose.

  Preferably, the total void volume is equal to at least 7% and at most equal to 12% of the volume equal to the sum of the total volume V of the tread and the total volume of the void.

  Preferably, the tread has an effective void volume Ve for each wear layer, which contributes to draining the contact patch where the tread contacts the road surface and satisfies the following equation:

                          0.4Se <Ve <0.8Se

In the above equation, 0.4 and 0.8 are heights expressed in millimeters (mm), and Se is defined by the outer contour of the contact patch where the tread is in contact with the road surface. E. tires T. T. et al. R. T. T. et al. O. Surface area (units expressed in mm ² ) measured under static conditions under the use (pressure and load) conditions described in the standard.
The effective void volume for each wear layer in this case refers to the void volume formed in the tread that helps drain the tread contact patch, and this effective void volume is subject to normal tire usage conditions. Determined.

  The wear layer of the present application means the portion of the tread associated with the maximum depth of the groove in the wear layer. The wear layer has a thickness that is less than the total thickness of the tread and is present in the wear layer or equal to the maximum depth of the cavity. The tread of the present invention has at least two wear layers and some of the grooves or cavities of these wear layers are formed in only one of such wear layers. Of course, in this configuration, each wear layer can be in an active state before the previous wear layer is completely worn away, which is advantageous, in which case at least two wear layers. There is an overlap between the layers. A wear layer is activated once the cavities or grooves formed in this wear layer are in contact with the road surface and open on the tread surface of the tire and become active and drain the water present on the road surface in rainy weather. To do. The first wear layer coincides with the tread portion located radially outward in the new state.

The heights of 0.4 mm and 0.8 mm may be present on the road in rainy weather and must be drained or picked up to maintain good contact between the tread and the road It means height. These average heights are taken into account in this case the surface area Se, ie the surface area defined by the contact patch profile of the tread on the same road surface and expressed in mm ² (surface area corresponding to the cavity opening on the tread surface) ) Can give an indication of the effective void volume Ve when the tire is subjected to normal use conditions (internal inflation pressure and supported load). If this void volume Ve is less than 0.4 times Se, it will not be sufficient to provide sufficient drainage and water will remain at the interface between the tire and the road surface. If this volume Ve exceeds 0.8 times Se, this volume is considered excessive in view of obtaining a suitable tread stiffness.

  According to a preferred modification of the present invention, the tread has at least one groove that is continuous and corrugated in the circumferential direction, and the at least one groove is a plurality that opens on the tread surface in a new state. Each of the open sections and a plurality of closed sections located entirely inside the tread in the radial direction so as to form a kind of first wear layer up to the radially innermost portion of the open sections. After this first wear layer, other wear layers extend into the tread depth to the innermost point of the inner cavity of the wear layer under consideration, and the open section is an average equal to at most 75% of the tread thickness. Having a depth, the closed section has an average height equal to at most 75% of the thickness of the tread.

  According to a preferred form, the minimum distance Dm of the bottom line of the wave motion is equal to at least 25% of the thickness of the tread.

  According to another preferred form of the invention, each corrugated groove has a constant or substantially constant surface area (which means that it refers to a surface area with a variation of at most 10%). Has a cross section.

  According to another advantageous embodiment of the tire according to the invention, all of the wear layers of the tread have the same composition.

  Other features and other advantages of the present invention will become apparent from the description given below with reference to the accompanying drawings, which illustrate, by way of non-limiting example, an embodiment of the present invention. Yes.

It is a figure which shows the step at the time of manufacturing the tread of this invention. It is a figure which shows the step at the time of manufacturing the tread of this invention. It is a figure which shows the step at the time of manufacturing the tread of this invention. It is a figure which shows the step at the time of manufacturing the tread of this invention. It is a figure which shows the step at the time of manufacturing the tread of this invention. It is a figure which shows the tread after shaping | molding and taking out of the insert which shape | molds the waveform groove | channel of this invention. It is a figure which shows the modification of the waveform groove | channel of this invention. It is a figure which shows the modification of the tire tread of this invention. It is a figure which shows the modification of the tire tread of this invention. It is a figure which shows the tread pattern of a prior art.

  1-5 illustrate the steps required in making the tread of the present invention.

  FIG. 1 shows a side 11 of a rubber unvulcanized band 10 having an outer surface 100 that becomes part of the surface of the tread after vulcanization and molding and an inner surface 101 that is arranged on the green tire. Show. The rubber band 10 has a height E corresponding to the thickness of the tread as measured between the outer surface 100 and the inner surface 101. On the side surface 11 of this band 10 of rubber, a groove 12 is formed that follows a corrugated line over the height E of the tread. This groove 12 is appropriately sized to receive an insert 4 similar to the insert shown in the example of FIG.

  The groove 12 has a corrugated shape and is continuous in the main direction of the rubber band. The groove 12 has a bottom line 120 that undulates between a minimum distance Dm and a maximum distance DM (a line connecting points on the bottom located farthest inward), and these two distances are determined by the outer surface 100. Measured with respect to. The groove 12 is flush with the outer surface 100 but can be located at a non-zero offset distance relative to the outer surface 100 to form a cavity filled with inserts.

  The groove 12 has an amplitude A equal to the difference DM-Dm, which is smaller than the thickness E of the tread, whereas the wavelength λ of the undulation wave of the groove is made by the tread using this rubber band. It is selected to be smaller than the average length of the contact patch of the target tire.

  2 and 3 are cross-sectional views of the rubber band 10 taken at the cross-section indicated by II-II and III-III in FIG.

  FIG. 4 shows the insert 4 adapted to be placed in the corrugated groove 12. The insert 4 is formed of a rubber skin layer 40 surrounding a core 41 made of a powder material.

  FIG. 5 shows a set of three rubber bands: a first rubber band 10 with an insert 4, a second rubber band 20 without an insert, and a third rubber band 10 ′ with an insert 4 ′. A solid is shown. The third rubber band 10 ′ is formed in the same manner as the rubber band 10, and the groove on the rubber band 10 is in the longitudinal direction with respect to the groove formed on the first rubber band 10 ( This is offset in the direction perpendicular to the plane of the figure.

  FIG. 6 shows the tread 2 after molding and removal of inserts each forming the corrugated groove 5 of the present invention. After vulcanizing and molding the rubber band stack shown in FIG. 5, the tread surface 200 of the tread 2 is exposed to expose the insert and thus remove the insert to form a continuous corrugated groove 5. It is easy to slightly machine the outer surface that has become. These corrugated grooves 5 formed near the side edges 21, 22 of the tread are formed by a series of open sections 51 that are open on the tread surface and joined together by a closed section 52 that penetrates the thickness of the tread. ing. The presence of the rubber bridge 210 between the tread surface 200 and these closed sections 52 ensures excellent mechanical resistance to striking and loading on the side edges of the tread. In this example, the skin layer 40 (shown in FIG. 4) of each insert 4 is held in place in the groove, and by using an appropriate material, such skin layer is resistant to potential cracking. It can be understood that it can be further improved. This skin layer forms the side wall 54 and the bottom 53 of the corrugated groove 5.

  In this particular case, the length of the open section 51 is greater than the length of the closed section 52 and the cross-section is substantially for each of the open section and the closed section to ensure optimal circulation of fluids, particularly liquids, in the new state. Are identical.

Thus, a heavy-duty vehicle tire having a tread 2 having a total thickness E and a total volume V, the tread having a tread surface 200 adapted to contact the road surface,
-Having at least one cavity or groove 5 continuous in the main direction, the cavity or groove 5 being defined by side walls 54 connected to each other by a bottom 53, the cavity or groove having a cross-section, each cavity The farthest point toward the inside of the bottom portion 53 of the base plate defines a bottom line 530,
-Each cavity or groove has a plurality of open sections 51 and a plurality of closed sections 52 that are open on the tread surface in the new state, and the closed sections connected to the open sections are arranged every other section. And each closure section is spaced from the tread surface by a rubber bridge, in the tire,
The location on the bottom line 530 of the cavity or groove is located at a distance between the minimum distance Dm and the maximum distance DM, and the distance measured on the tread in the new state relative to the tread surface is At most equal to the total thickness E,
The bottom line 530 of each cavity or groove is equal to the difference in the positive amplitude (DM-Dm) and for the new tire T. T. et al. R. T. T. et al. O. Follow the waveform geometry along a wavelength shorter than the average length of the contact patch measured under the conditions of use specified in the standard,
A rubber bridge 210 formed between each closed section 52 and the tread surface 200 is continuous, ie a tire is obtained which is not provided with a cut connecting the tread to the closed section. .

  FIG. 7 shows a corrugated groove 5 as a modification of the present invention. According to this variation, the corrugated groove 5 has several consecutive height positions, and the bottom line 530 is a first position located a distance DM1 away from a position located at a distance Dm from the tread surface. And a second position located a distance DM2 apart, and the distance DM2 is greater than DM1. The total groove amplitude A in this case is equal to the difference DM2-Dm. This wave wavelength λ, which is equal to the distance between two consecutive open sections on the tread surface, at least partially defines two open sections for each corrugated groove in the contact patch in contact with the road surface. The tire is selected to be shorter than the average length of the contact patch in contact with the road surface when operated under normal use conditions. Each height position defines one wear layer of the tread.

  FIG. 8 shows a tread 3 as a modified example of the tire of the present invention, and this tread is obtained using the method just described in connection with FIGS. The tread 3 shown in cross-section (i.e. a cross-section in a cross-sectional plane containing the axis of rotation of the tire) has a tread surface 30 that comes into contact with the road surface during operation. It is bounded by a side wall 31. The tread 3 has two grooves 32 having a depth equal to the thickness of the tread, and these two grooves 32 are in contact with the sipe 61 and are substantially as extension portions of the sipe. A channel 6 is provided which is adapted to form a new groove after partial wear representing half the thickness of the tread. The channel 6 extends at a maximum depth equal to the depth of the groove 32.

  Furthermore, the tread has a continuous corrugated groove 5 in the circumferential direction (longitudinal direction) on the outer side in the axial direction of each groove 32. Each corrugated groove has a plurality of open sections opened in the tread surface and a plurality of closed sections similar to the closed sections described in connection with FIGS. Thus, it is possible to reinforce the side edge of the tread while enjoying the beneficial effects of the drain. Following partial wear, these corrugated grooves 5 form cavities that are not connected to each other, and the opening of the channel 6 to the tread surface can restore some of the tread drainability.

  FIG. 9 shows a tread 7 as a modified example of the tire of the present invention which is quite close to the configuration shown in FIG. In this particular case, a groove 72 is formed having a depth that is less than the thickness of the tread (which means that the tread is less than the thickness that can be worn before reaching the legal wear limit). .

  A corrugated and continuous groove 5 is formed on the edge meaning that it is the axially outer side of each groove 72, and this groove has a plurality of open sections that open to the surface of the tread in the new state. The maximum depth (DM) of these corrugated grooves is equal to the thickness of the tread.

  A continuous cavity 5 "is formed in the central part of the tread 7, which is corrugated in the depth of the tread and filled with the insert 4" at the time of manufacture. This insert is a tread. When wear reaches the insert, it no longer forms new and continuous corrugated grooves (in an alternative embodiment, the insert is a tube filled with powder material that disappears when the tire is rotating. Preferably, the insert becomes visible before the open section of the continuous and corrugated groove 5 formed on the edge portion of the tread is completely worn out.

  All of the above examples use a single rubber compound, but it should be understood that the composition should be set to suit each wear level. Similarly, the tread illustrated in a simple manner may further have lateral grooves, which are of a depth equal to the thickness of the tread or alternatively are corrugated and circular. It can be of the same corrugated appearance as the circumferentially directed grooves.

  Naturally, the invention is not limited to the embodiments shown and described, and various modifications can be made to these embodiments without departing from the scope of the invention as set forth in the claims. . In particular, the entire description herein relates exclusively to the use of tires adapted to be attached to heavy-duty vehicles, but it should be understood that tread patterns and compositions as specified herein are The tread which has also forms the principal part of this invention. This is because such a tread is incorporated into the tire (either at the time of tire manufacture or during regeneration). Further, when the corrugated cavity is formed in the thickness of the tread, the corrugation may be generated in a direction that coincides with the width direction of the tread.

  The described embodiment shows two wear layers, and it is understood that a greater number of wear layers can be provided and the same groove can penetrate these wear layers. .

FIG. 10 is a plan view of a prior art tread 9 corresponding to size 315 / 70R22.5. E. for tires of this size when mounted as a single wheel. T. T. et al. R. T. T. et al. O. The usage conditions defined by the standard are as follows: the inflation pressure is 9.00 bal, and the load per tire is 3750 kg.
In the case of the tire in question, this tread 9 has five longitudinal grooves 92 with a depth equal to the thickness E of the tread of 15 mm, which thickness is a material that has become worn during operation. Is consistent with the thickness. The tread further includes a groove directed laterally.

In the initial state, corresponding to a new and unworn tread, the total void volume of the tread available in the contact patch that can contact the road surface is large, measured under specified inflation and load conditions, and In this particular case, it is equal to 100 cm ³ . This volume is measured under conditions of use as described above under static conditions.

  In this particular case, there is only one wear layer. This is because the entire void volume formed by the longitudinal grooves is open to the tread surface in its initial state (new tire), and this void volume decreases as the tread gradually wears. It is.

  This tread has a total void volume equal to 19% of the total volume of the tread designed to wear.

  All the grooves have a depth equal to the thickness of the tread.

The effective void volume Ve of this tread is a surface area St (corresponding to the surface area defined by the outer contour of the tread contact patch measured at a height equal to 1 mm under static and normal pressure and load conditions. greater than the volume obtained by multiplying (expressed in mm ² ).

  For this tread, the effective void volume VE that drains water within the installation patch that can contact the road surface in a single wear layer is equal to 100% of the total void volume Vt of the tread. This is because all voids open onto the tread surface of a new tire.

  As noted, this traditional structure of the tread pattern necessary to obtain satisfactory drainage performance in the new state and until the tread reaches the wear limit is extremely high in the initial state (if the tread is new). High and consequently imposes void volume ratios that result in reduced stiffness (compression and shear stiffness) that can only be compensated for by the partial use of suitable materials and the use of such suitable materials.

  The invention described herein allows the tread to be more rigid by providing a large amount of material, especially when the thickness is the same, and thus particularly good for hitting the side edges of these treads. Tolerance is achieved.

Claims (10)

A heavy-duty vehicle tire having a tread (2) having a total thickness E and a total volume V, the tread having a tread surface (200) adapted to contact a road surface,
-Having at least one cavity or groove (5) continuous in the main direction, said cavity or groove (5) being defined by side walls (54) connected to each other by a bottom (53); The groove has a cross section, and the point located furthest toward the inside of the bottom (53) of each cavity defines a bottom line (530);
Each cavity or groove has a plurality of open sections (51) and a plurality of closed sections (52) open on the tread surface in the new state, the closed sections connected to the open sections being , In the tire, arranged in every other place, each closed section being spaced from the tread surface by a rubber bridge,
The point on the bottom line (530) of the cavity or groove is located at a distance between the minimum distance Dm and the maximum distance DM, and measured on the tread in the new state with respect to the tread surface The distance made is at most equal to the total thickness E of the tread,
The bottom line (530) of each cavity or groove is equal to the difference in the positive amplitude (DM-Dm) and for a new tire T. T. et al. R. T. T. et al. O. Follow the waveform geometry along a wavelength shorter than the average length of the contact patch measured under the conditions of use specified in the standard,
-The rubber bridge formed between each closed section (52) and the tread surface (200) is a continuous tire.   The tire of claim 1, wherein the minimum distance Dm between the bottom line (530) of the corrugated groove and the tread surface is equal to at least 25% of the total thickness E of the tread.   The tread has at least one insert (4, 4 ', 4 ") adapted to form a cavity which is continuous in the main direction, the cavity being defined by side walls connected to each other by a bottom. The farthest point toward the inside of the bottom of the cavity defines a corrugated bottom line, and the inserts (4, 4 ', 4 ") only when the tread is partially worn 3. Tire according to claim 1 or 2, arranged in the tread in such a way as to appear on the tread surface.   The bottom line of the cavity with the insert (4,4 ', 4 ") is the average of the contact patches measured under the conditions of use described in the ET RTO standard for new tires The tire of claim 3, following a corrugated geometry having a wavelength shorter than the length.   Tire according to any one of the preceding claims, wherein each corrugated groove (5) is defined by a wall formed in a material different from the constituent material of the tread.   Each insert (4 ') is surrounded by a material that is different from the constituent material of the tread, such that the material remains connected to the tread even after the insert is removed, The tire according to claim 3.   4. Tire according to claim 3, wherein each insert (4 ') is in the form of a hollow tube.   8. A tire according to claim 7, wherein each hollow tube is made of an elastomeric material, the hollow tube comprising means for maintaining pressure in the tube during molding. A method of obtaining a tread (2) having at least one continuous corrugated cavity or groove (5), said method comprising:
-Adjusting the unvulcanized band of rubber;
-Incorporating at least one insert (4,4 ', 4 ") into the rubber band with a geometric shape that is corrugated at least in the depth of the tread;
-Forming and vulcanizing the tread band;
-A method of obtaining a tread (2) comprising at least partially removing each insert (4, 4 ', 4 ") to form at least one continuous corrugated cavity or groove (5).   The incorporation of at least one insert (4,4 ', 4 ") in a geometric shape that is corrugated at least in the depth of the tread causes each insert (4,4', 4") to be inserted into the tread. 10. A method of obtaining a tread (2) according to claim 9, carried out by using an extruder equipped with means that can be appropriately positioned in the thickness.

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